semigroup.ts

const getLongestSemigroup = <
  A extends { length: number } = never
>(): S.Semigroup<A> => {
  return { concat: (x, y) => (x.length > y.length ? x : y) };
};

const getLongestOptionSemigroup = O.getMonoid<Unit>(getLongestSemigroup());
    
const longestString = getLongestOptionSemigroup.concat(
  string1Opt,
  string2Opt
);